dazygirl415

Exactly!!!!! Jessie and I went to the liquor store tonight and unless I was in neutral or just letting off the gas, all conversation was pointless. As was the radio.

dazygirl415

Question: Am I gaining any HP from this? And how much weight will a straight pipe add compared to the stock exhaust?

jenkins-crew

wont add weight, should be lighter than stock.

jenkins-crew

you might get a little more HP because of a more free flowing exhaust with no mufflers.

Ajax

I doubt you're gaining any noticeable HP.
The exhaust is mostly just changing the sound. The problem with the RX8 exhaust is not the stock exhaust, but the stock exhaust ports/headers.

jenkins-crew

and the restictive CAT

Ajax

well, the CAT is restrictive, but not nearly as much as the size and shape of the exhaust ports and moreso of the exhaust headers.. even if you open up the exhaust ports, those headers are a major problem. The siamesed center exhaust is also crappy. Two lines sharing a single header with a divider cannot possibly flow enough exhaust gas out of the engine..

jenkins-crew

this is true.

jenkins-crew

I say just put the greddy system on Tiff, you might loose money on restocking and return fee's. Youll get tired of it being loud after awhile if you go the custom way, unless you add some resinators to it.

Ajax

I knew I missed something! lol. I didnt notice that you said you hadn't put the exhaust on yet.

Duh! no wonder it's so loud.

Scalliwag

Yep the siamesed ports are pretty jacked up. That was used in the Pontiac V8's of which most of my background was around; GTO's and Firebirds/ Trans Ams.
They used what was called a "D port" on the two center cylinders of each head.
But in the case of those was that not only was there the inherant problem of exhaust pressure transferring to opposing cylinders that were not at the exhaust stroke at the time themselves, but they were also trying to force the exhaust through smaller ports There is a Pontiac head called a "Ram Air IV" with round center ports. Check the price on those sometime
At least with the side ports on each side of each rotor chamber there is another escape route at the front and rear side plates for the exhaust to escape.

The best case scenerio I can see for the center exhaust would be to machine a plate (shaped like an exhaust gasket) with a separator plate in the middle that protruded into the exhaust manifold as far as you could get it.
The Renesis center plate exhaust port they even added insult to injury because the separation between the two chambers does not even stop flush with the edge of the housing. So not only would the divider plate have to protrude into the exhaust manifold as far as possible but it would have to protrude a little back into the side plate as well or you would have about a 1/4" gap.
You you help the situation alot more if the plate only protruded into the the plate to fill that gap and then had a custom header with seperate center tubes.

The first person to get a Renesis motor we can bring here to the shop will be my "bestus friend" :D I will get Brian Cain to polish out the ports and I will make such a plate and possibly the header. The apex seals are so short I would want to slot them deeper to accept the older 2 piece seals and springs as well.
Between all that and having the entire rotating assembly balanced it would be very interesting what effect on the HP it would have.
It should not effect the stock ECU. But I do wonder since I am pretty sure that the EGR effect caused by the siamesed porting might throw it off

I have an open engine stand just waiting if one of you want to give it a try

dazygirl415

OK. I did my best to follow and I think I kinda understand. But the expression on my face is the same as it was when you lit the grill with the blow torch.

Ajax

Lol. Directions to your shop?

Openning the exhaust ports does definitely affect the ECU unfortunately. The ECU is constantly monitoring exhaust temperature and AFR in open loop. As we saw with stock tuning, the car in open loop actually made the AFR RICHER when it had more air flow in and out.

The exhaust header (for the entire exhaust) is what needs to be done. As far as the seals go, the seals on the renesis are very very strong. Yes, they have more clearance than any seals in the past, but I do wonder if they were designed that way for a reason?

There is of course 1 more thing you should DEFINITELY do if you open an engine and that is polish the edges of the primary and auxiliary ports. The top edge of those ports is RAZOR sharp and definitely needs to go.

Scalliwag

Haha! I didn't think anyone had a lighter and I was getting really hungry I saw the torch, grabbed the striker, and "WALA!!!" we were ready to throw meat on the barbie!!!

Brian said he is in on for doing the polish work if somebody can come up with a motor So, ummm Dazy, do you have alternate means of transportation for a few weeks?

NYT-OWL

I would almost be willing to let you try it out on mine. I've gone beyond the 50k miles and am already out of the warranty. However, this is my daily driver and unless I get another mode of transportation (currently looking into that) I would hate to have something screw the car up to where I couldn't drive it. Also another thing of question would be since the motor normally runs pretty rich from my understanding, what would this do as far as passing state inspection?

dazygirl415

I see that my 8 has become the one everyone wants to experiment on. Let me think about that one Scalliwag and I'll get back to you.

Ajax

Wow. You drive a lot.

As long as you don't put any overlap into the port timing, you should have no worry about inspection. The car runs rich as is. Openning up the exhaust and intake will most likely give you better power as well as gas mileage as the exhaust is entirely too restrictive.

Tuning it properly will give you even more power and you might lose a little of that mileage, but still be well within inspection levels. Your CAT probably wouldnt last as long, but who wants a CAT anyway? It'd run a bit warmer so it'd actually catalyse faster at start up (and wear out faster).

The stock ECU is a pain in the butt though.

Scalliwag

Ken Scheepers ran a set of Renesis rotors in one of the race motors. They made it half way through the first pull on the engine dyno at RP They aren't tall enough and flex a little in the center at high rpm
Don't get me wrong for stock use they work. I wanna rap that bitch to 11k though :D
I am not really wanting to open the exhaust as much as clean any casting imperfections and and mainly polish the hell out of them. You have seen BDC's polish work I'm pretty sure Ajax?
Trying to tweak it to the extreme that would not go out of range on the ECU is more my goal. Of course a full exhaust fix would be ideal. But if I could make a plate that could boost the HP up some that was only a matter of pulling the exhaust manifold back, putting a gasket on, slipping the plate in and adding the extra gasket it would be a good marketable item. At least that would be the projected goal

Ajax

He ran ren rotors in a non renesis housing? From what i've heard, putting those rotors in any other housing will tear the **** out of the housing. They're balanced totally differently than older 13b rotors.
BDC's polish work is really good.
I'm not interested in going that extreme myself. I'm not building a race car either tho :b
The stock flywheel (and most of the aftermarket flys) is not even rated to handle more than 9500 rpm.. same with the clutch and tranny. Who knows about the driveshaft or differential?

What I am interested in is optimizing the power of the renesis engine while maintaining relative driveability. No full bridge ports for me. Bridge porting the aux ports is intriguing though as that would not impact drivability at all. What I'm thinking is open the exhaust as much as necessary, all the way back to the headers. Fix the siamesed center port issue if possible. Mild street port on the primary ports then either large street port on the aux ports or bridge port them like i mentioned above. See what that does and if it's still not at least 250 rwhp, drop a GT35 turbo on there, run about 9psi and see if I can get 350 at the wheels. (have to put larger injectors in there for that too tho)...

jenkins-crew

I know there are lots of wrecked 8s out there you could probably get an engine to play with.

Scalliwag

RIght now there are so many pieces of equipment and other things we want/need at the shop I can't justify the short-term purchase on one. As much as I would like to. It would be better for me to do the work for someone else if it happened within the next 3 months at least.

Scalliwag

Here is a pic of one of the things we did NOT eat this weekend N-O Oh, I found two more of the females are having babies. What is 500-800 babies X3?

Mr. Ed's rx-8

you know if yo clean up that shop and get it all in order...i'm buying a daily driver. i might be willing to put my car out there for some port testing. as long as it is going to still run. i realize the risk but its my baby!

maybe we can talk more this tuesday night. i'm just waiting on my tax return to come in then i plan on buying a little beater car. so if anyone knows of a good running car for a round a grand, i don't care what it looks like as long as it runs good. let me know!

oh and scalliwag, can i still buy that laptop?

Scalliwag

Well David and/or his guys have to clean up and organize the east shop and we will be in good shape. That and a few less cars on that side. Like you said we can get into more detail on what you are up to doing to it. Brian Cain is excited about polishing it out and looking it over.
We will see if James can get you some pulls on the dyno at Alamo before we start and then get some afterwards.

I will check a couple of friends and see what they may have on a daily driver for you.
And yes I will have the laptop for you on Tues. I can get another bag for $20 if you want one. Just let me know.

Ajax

where is that shop anyway?